The interior statement may contain one or more media statements. Media is used to
simulate suspended particles such as smoke, haze, or dust. Or visible gasses such as steam or fire and explosions.
When used with an object interior, the effect is constrained by the object's shape. The calculations begin when the
ray enters an object and ends when it leaves the object. This section only discusses media when used with object
interior. The complete syntax and an explanation of all of the parameters and options for media is given
in the section "Media".

Typically the object itself is given a fully transparent texture however media also works in partially transparent
objects. The texture pattern itself does not effect the interior media except perhaps to create shadows on it. The
texture pattern of an object applies only to the surface shell. Any interior media patterns are totally independent of
the texture.

In previous versions of POV-Ray, this feature was called halo and was part of the texture
specification along with pigment, normal, and finish. See "Why
are Interior and Media Necessary?" for an explanation of the reasons for the change.

Media may also be specified outside an object to simulate atmospheric media. There is no constraining object in
this case. If you only want media effects in a particular area, you should use object media rather than only relying
upon the media pattern. In general it will be faster and more accurate because it only calculates inside the
constraining object. See "Atmospheric Media" for details on
unconstrained uses of media.

You may specify more than one media statement per interior statement. In that case, all
of the media participate and where they overlap, they add together.

Any object which is supposed to have media effects inside it, whether those effects are object media or atmospheric
media, must have the hollow on keyword applied. Otherwise the media is blocked. See "Empty
and Solid Objects" for details.